Electric control circuit



B. COOPER ETAL 2,373,545

ELECTRIC CONTROL CIRCUIT AprillO, 1945.

Filed Nov. 1, 1945 4 Sheets-Sheet 1 Fig. l a

1 I nvent ors Benjamin Cooper, Orrin Livingston,

Their- Attorney.

April 10, 1945.

B. COOPER ETAL ELECTRIC CONTROL CIRCUIT Filed Nov. 1, 1943 4 Sheets-Sheet 3 lnventor s; Benjamin Cooper, Orrin W. Livingston,

Attorney.

April 10, 1945; B. COOPER r AL ELECTRIC CONTROL CIRCUIT Filed Nov. 1, 1943 4 Sheets-Sheet 4 SUPPLY l8 UFF TIME Fl ON TIME FILAM SUPPLY n r0 at MAW rw n m om wr o ?w 4 v .6 mmw M mm a Br 0 Y Fatentel Apr. ill, 2

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Benjamin @ooper and Uri-in Livingston, Scotia, Nu lZ.,' assignors to General Electric "Jonopany, a corporation oil New Kori:

duplication Novernher ll, 194.3, Serial No. 5ll8l (Ci. Bill-119) Uur invention relates to electric control circuits voltage icy means including a, phase shift circuit and particularly to improved regulating circuits controlled loy variations in the output of the regespecially adapted for regulating the current supulator circuit with respect the voltage of the ca= plied to an intermittently energized load circuit pacitor which was charged during the immedi- In the application of electric valves to resist- 5 ately preceding period of energization. In ance welding circuits, some diiiiculty has been exway, the circuit may he considered to operate as perienoed in regulating the current supplied to an on-time current regulator and an ofi time the welding transformer, particularly with revoltage compensator with the compensation for spect to controlling the magnitude of the current source voltage changes being accomplished with during the first cycle or cycles of each period of reference to the voltage ero'sting at the end of energizatlon. Our invention relates to an imthe preceding period-oi? energization.

proved regulating circuit particularly adapted for Our invention will he better understood by reireguating the current supplied to intermittently erence to the following description taken in conenergized loads and which insures a substantially nection with the accompanying drawings, and its uniform supply of current to the load circuit durscope will he pointed out in the appended claims. ing each cycle of the periods of energization, In the drawings l igs. lo and it considered to- Our invention is in the nature of an irnprovegather are a schematic representation of one eroinentover the systems described and claimed in sediment of our invention, and Figs. 2c and 2h Livingston Patent No. 2,355,453, dated August 3, are a' schematic representation of another cinl94 l, and Cooper application Serial No. 480,150. hodiment of our invention.

fled March 28, 1943. The Livingston patent and Referring now to Figs. lo and lb or the draw- Cooper application are assigned to the assignee ings, we have shown our invention embodied in of the present invention and are to be consida regulating circuit for controlling the magnitude cred prior art with respect to the invention of of the current supplied to a welding transformer this application, ill from an alternating current supply circuit ll It is an object of our invention to provide a new through a pair oi reversely connected electric and improved electric control circuit. valve means it and it. The electric valve means It is another object or" our invention to provide may he of the type employing an immersion-iga new and improved regulating circuit for eonnitor control member and a liquid cathode or, as trolling the magnitude of the current supplie illustrated, may comprise an anode i l, a cathode to an intermittently energized load circuit. it. a control grid it and a shield grid i The it is still another object or" our invention to electrodes are enclosed in an envelope containingprovide a new and improved control circuit for an icnizahle medium, such as a gas or a vapor. regulating the magnitude of the alternating cur- The excitation circuits for electric valves l2 and rent supplied to an intermittently energized load 3? it are identical so only one will he described, and which insures uniform energization of the load the same reference numerals will he applied to circuit throughout each interval. corresponding parts. Referring to the electric In accordance with one illustrated embodiment valv i2, the control member ll thereof is conor our invention we employa pair of reversely nected to the cathode through an excitation circonnected electric valve means for supplying encult including a current limiting resistor iii, a

- ergy from an alternating current supply circuit to secondary winding l 9 of a transformer 20, a see-- a, resistance welding transformer. The electric ondary winding 2i oi a transformer 22 and a.

valves are rendered conductive intermittently secondary winding 23 or a transformer 24. The under the-control of a timer and the instant of secondary winding 2i impresses an alternating initiation of conduction during each cycle of each current voltage on control member l8 which is in period of energlzation is controlled by an imv phase opposition to the anode voltage thereof to proved regulating circuit. During each period of render the electric valve nonconductive. The energization, the regulation is accomplished dicycles during which the electric valve may be renrectly in response to the welding current. Durdered conductive are determined by a timer conlng this same interval a capacitor is charged to trol illustrated generally by the numeral 25 which a voltage dependent upon the phase position of is energized from the alternating current supply the excitation voltage of the electric valves. Durcircuit ll under the control of an initiating ing a, period of deenergization following a period switch 26, and which impresses an alternating of energization, the regulating circuit is variably current voltage on the primary winding 2'7 of the energized in accordance with the supply circuit transformer 24 during those periods that the load illustrated generally by the numeral 30.

of valves 3| and 32 through resistors 46.

is to be energized. The voltage of the secondary winding 23. is in phase with the anode voltage of the electric valve |2 but is insufficient in magniture to overcome the hold-off voltage impressed on the control member by the winding 2|. The primary winding 28 of the transformer 20 is energized by the output of a phase shifting circuit illustrated generally by the numeral 29 which determines the phase of the peaked voltage induced in the secondary winding I9 of the transformer 20 to determine the instant in the anodecathode voltage wave of the valve |2 at which conduction is initiated. In other words, the timer control 25 and transformer 24 determine the duced in the secondary windings IQ of transformer 2!] and as a result the magnitude of the current supplied to the welding transformer is determined by the phase Shifting circuit 29 which is controlled by the output of a regulating circuit The phase shifting circuit includes a pair of electric valve means 3| and 32 which are connected to energize the primary winding 28 of transformer 23 with voltage impulses at instants determined by the operation of the regulating. circuit 30. The

electric valves 3| and 32 are, as illustratedfpreferably of the type employing anionizable medium, such as a gas or a vapor, and each comprises an anode 33, acathode 34, a control grid 35 and a shield grid 35. The cathodes of electric valves 3| and 32 are connected together and'the anodes thereof are connected, respectively, with the end terminals of a mid-tapped secondary winding 31 of a transformer 38 having a primary winding 39 thereof energized from the alternating current supply circuit The mid-terminal of the transformer winding 33 is connected to the cathodes of electric valves 3| and 32 through resistors 4,0 and 4| connected in series. The primary winding 28 of the peaking transformer 20 is connected across the terminals of resistor 4| and resistance 40 serves as a means of adjusting the magnitude of the voltage peaks produced byv transformer secondary windings l9 when the electric valves 3| "and 32 are rendered conductive.

Thus, the phase shifting circuit 29 provides a means for shock exciting the primary winding of the peaking transformer 20 to produce voltages of peaked wave form at instants in the supply circuit voltage wave determined by the instants that the electric valves 3| and 32 are rendered conductive. Referring to the drawings, the initiation of conduction in the valves 3| and 32 is controlled by an excitation circuit including the output conductors 42 and 43 of the regulating circuit 30 and the secondary winding 44 of a transcurrent supply circuit through a secondary winding 41 of the transformer 38 and a phase shifting means including a capacitor 48 and an adjustable resistor 49. The capacitor 48 andresistor 49 are connected in series across the end terminals of transformer winding 41, and the primary winding of transformer is connected between the common terminal of the resistor and capacitor and the midtap of transformer winding 41.

During the periods that the load circuit is energized, the regulating circuit 30 functions to produce a variable unidirectional voltage across the conductors 42 and 43 inresponse to variations in the current supplied'to the load circuit. The portion of the circuit which functions during the on time will now be described. A supply of unidirectional voltage for the regulating circuit 30 is impressed on the conductors 50 and 5| from the output of "a full wave rectifier which comprises a gaseous discharge device 52 and a midtapped secondary winding 53 of the transformer 38. The output of the rectifier is filtered by a series reactor 54 and a parallel capacitor 55. -A resistor 56 and voltage regulating discharge devices 51, 58; 59 and 60, preferably of the cold cathode type, are connected in series between the conductors 50 and 5| to establish different levels of direct current voltage for the regulating circuit. These voltages appear on conductors 6| 42, 62 and 63. In order to render the regulating circuit 30 responsive to the heating value of the current supplied to the load circuit, we employ a regulating electric valve illustrated as an electric discharge device 64 having a filamentary-type cathode which is variably energized in accordance with the magnitude of the load current. The filament is energized bythe voltage of the secondary winding 65 of a transformer 66 having a privoltage appearing between the terminal 59 and --conductor 63 is impressed on the control member. of an amplifying valve 10. The cathode of the'electric valve 10 is connected with the conductor 63, and the anode is connected with the conductor 6| through a load resistor II. The control member of the valve 10 is connected through a. current limiting resistor 12 and a second resistor 13 to the output terminal 69 of the former 45 which provides an alternating current component of grid voltage which lags the anode voltage of electric valve 3| and 32 by approximately 90 electrical degrees. Conductor: 43 is connected with the cathodes of electric valves 3| and 32, and the conductor 42 is connected to the mid-point of the transformer secondary winding 44. The end terminals of the winding 44 are connected respectively with the control members 35 The bridge circuit. The control member of the valve 70 is connected with the anode thereof through a series capacitor 14 and resistance I5 which serve to suppress transient voltages on the control member. The output conductors 42 and 43 of the regulating circuit 30 are connected, respectively, with the common terminal of discharge devices 51 and 58 and the anode of amplifying valve 10 so that the direct current voltage appearing between I conductors 42 and 43 varies in accordance with may operate, we provide a circuit including volt= age dividing resistor it connected across the terminals of discharge device '1] and a discharge device it having the anode connected to the anode of th regulating valve is and the cathode connected with an adjustable point on the voltage dividing resistor it. As the conductivity of the regulating valve it is decreased, the'anode of the electric-discharge device it becomes more positive and at a predetermined point, dependent upon the position or the adjustable tap on the voltage dividing resistor will be rendered conductive to connect the conductor 33 directly with the voltage dividing resistor it.

The circuit for energizing the filamentary cathode of the regulating electric valve 661 during the periods of energization of the load circuit will now be described. The primary winding (ll of the transformer the secondary winding 65 of which energizes the filamentary cathode of the regulating valve $5, is connected to be energized in accordance with the current conducted b a of electric valves l8 and it of a circuit designated on-time filament supply. The anodecathode circuits of electric-valves l8 and is are energized by means of transformer secondary windings and ill with a voltage having a magnitude dependent upon the magnitude of the current supplied to the welding transformer. The windings St and ti are the secondary windings of a transformer having the primar winding thereof energized from a current transformer 85 associated with one of the supply lines to the welding transformer. The magnitude of the voltage induced windings Bill and ill for a given current in the'welding transformer is controlled by an adjustable tap 35 on the primary winding and by adjustable loading resistors 86 and 355d which are connected across the transformer priof welding heat and resistor 86a and tap 85 may be adjusted so that the resistor 86 covers the desired 1 range. One terminal of the secondary winding til is connected with the anode of electric valve its; and the other terminal is connected through a conductor to an end terminal of the transformer winding 3'5. The mid-terminal of this winding is connected with the cathodes of electric valves lit and "1e through a conductor In a similar manner, the secondary winding St has one terminal connected to the anode of electric valve ill and the other terminal connected through a conductor lit, the other half of the transformer winding el, and the conductor to to the cathodes of electric valves it and to. Thus the anode voltage of electric valves it and it, and as a result the voltage impressed on the primary winding of transformer (i5, varies directly in accordance with the magnitude of the load current. Electric valves ill and iii are rendered conductive for the "full period of energization of the welding transformer by means of a midtapped secondary winding of a transformer ill having a primary winding connected directly across the primary winding of the welding transformer. The end terminals of the winding 9d are connected to the control members of electric valves it and l9 through current limiting resistors $32 to impress on the control members an alternating current voltage which is in phase with the anode voltage impressed on these valves by the transformer windings tit and ti.

With this arrangement for energizing the filamentary cathode of the regulating lectric valve 6 1 there is an appreciable ripple voltage in the unidirectional voltage appearing between conductor it and terminal forming the output of the regulating bridge. For this reason, we provide means for eliminating this ripple so that a pure direct current regulating voltage may be impressed on the amplifying valve it. We accomplish the elimination of this ripple by impressing across resistor la a voltage of the same character as the ripple voltage in the output circuit'of the regulating bridge but of opposite phase relation. The ripple voltage across resistor '53 is derived from the output of a full wave rectifying circuit comlzvrising an electric valve 9 3 having a pair of conducting paths associated with the end terminals of a midtapped transformer winding of the transformer Since the transformer winding 95 is energized in the same manner as the'secondary winding which energizes the filamentary cathode of the valve t l, it is possible to produce a ripple voltage in the output circuit of the valve 9d which will cancel the ripple voltage produced by regulating valve t l. The'cathode of the valve lid is connected through a'resistor as to an output circuit including a parallel resistor ill and a capacitor 98. The voltage appearing across resistor 97 is impressed on resistor 3 through a coupling capacitor 99 which isolates the two circuits, so far as direct current voltage is concerned, and passes only the ripple voltage which it is desired to impress across the terminals of resistance l3.

The circuit thus far described constitutes the current regulating system which functions during the periods of energization of the load circuit. In order to have the regulator conditioned for regulating action during the first cycle of each period of energizationit is necessary to provide some means for energizing the filamentary cathode of the regulating valve 66 during the off periods. In accordance with'our invention, we

provide means for establishing a voltage duringthe on period which is used as a reference voltage for regulating action during the off period.

Referring now to the drawings, we provide a capacitor llld which is connected in series with the anode-cathode circuit of an electric valve till and across the direct current voltage supplied between the conductors and 83. The electric valve till is preferably of the high vacuum pentode type in order to render the charging rate of capacitor llill substantially independent of fluctuations in the anode-cathode voltage of the valve. The control grid ill? of the valve tilt is energized in accordance with the output voltage of the amplifying valve ill of the regulating circuit'b-y conductor lllil which is connected with the output conductor 63 through a suitable resistor Mi l. The cathode of the valve llll is connected to the common terminal of voltage dividing resistors ill? and H36 through a resistor llliic. lhe voltage dividing resistors tilt and llld are connected across the direct current supply terminals 59 and 63, In order to establish a voltage for the screen grid of the pent-ode ldl whichis substantially constant with respect to the cathode voltage, we provide a voltage regulating discharge device l t'l which is connected in series with a resistor Hi8 and. across the conductors 5d and $3. The screen grid is connected with the common terminal of the regulating valve l8? and the resistor llld. Thus the capacitor tilt is charged during the on time to a voltage dependent upon the output of the regulating circuit 36, which'is a measure of the phase position of the excitation to permit the discharge of capacitor I during the 'on time in the event that the conductivity of electric valve "II is decreased, a discharge circuit across the terminals of capacitor I00 is provided by means of an electric valve means I09,

preferably of the high vacuum type, having an anode H0 and a cathode III connected in series with resistor H2 and acrossthe terrninalsof the capacitor I00. The electric valve means IDS is provided with a second discharge path including an anode H3 and a cathode IIG which connects the control grid I02 of electric valve IOI with the direct current supply conductor 83. Thus when the discharge path including anode I I3 and cathode II4 is conductive, the control member of electric valve IN is maintained at a negative I voltage and the valve IIlI is rendered nonconducting. QThe conductivities of the discharge paths of electric valve means I00 are controlled by control grids H5 and 6 which are energized in accordance with the conductivity of a switching electric valve means III which is similar in construction to the electric'valve means I09 and is controlled in accordance with the periods of energization of the load circuit. The electric valve means H? is provided with a pair of discharge paths, one of which includes the anode I I8 and the cathode H9 and the other of which includes anode I20 and cathode I2I. The cathodes are connected together and to a point of voltage intermediate the voltage of conductors 63 and 5i established by a voltage divider including resistors I22, I23 and I241. The anode H8 is connected to conductor 52 through a resistor I25, and the anode I20 is connected with the conductor 82 through a resistor I25. The control rid II5 of electric valve means I03 is connected with the anode I20 through a current limiting resistor I27, and the control grid H6 is con'-,

nected with the anode IIB through a current limiting resistor I28. From an inspection ofthe drawings and a consideration of the relative potentials of direct current conductors BI, '62 and 33, it will be apparent that the left-hand dis-' charge path of electric valve I03 will be conductby control grids I23 and I30 which are energized in accordance with the periods of energization of the load circuit by means of a secondary winding I3I of the transformer 9I which is energized in accordance [with the voltage of the welding transformer. The secondary winding I3] is provided with a midtap and provides the power supply for a full wave rectifier including an electric I discharge device I32 which is connectedto produce aunidirectional voltage across a resistor I33 and parallel capacitor I34 during the periods that the welding transformer is energized. The grid I29 controlling the discharge in the left-hand path of the electric valve means I I1 is connected with the cathodethrough a current limiting resistorI35, resistor I33, and the voltage dividing resistor I24 which supplies a component of negative bias. When the welding transformer is de- The conductivities of the discharge.

energized, 'no voltage appears across resistor I33 and the left-hand discharge path of valve IIl is maintained nonconductive by the negative bias of resistor I24. During this period, the grid I3llof the right-hand discharge path of the elec tric valve H1 is maintained suficiently positive with respect to the cathode by the connection of the control member I30 with the terminal I35 of voltage dividing resistors I3? and I38. It will be apparent that the voltage of the control grid I30, during periods of nonconduction of the lefthand electric discharge device III, may be suitably adjusted by a proper selection of voltage dividingresistors I37 and I30. Conduction by the left-hand discharge path of electric valve means Ill is also effective to render an electric .discharge. device I39 conductive to render negative the excitation voltage of the control members of-the oil-time filament supply, illustrated generally by the numeral I40. The operation of this circuit will be described in more detail at a later point in the specification.

As previously described, .the capacitor I 00, which may be considered a memory-capacitor, is utilized to establish a voltage at the end of each period of conduction which is a measure of the phase position of the excitation voltages supplied to 'the control members of the electric valve means connected in the supply circuit of the welding transformer. 1 During the off period,

the output of the regulating circuit 30 is compared to this voltage and impressed on an o time phase shifting circuit, designated gener-;

ally by the numeral I4l through an amplifier 1/? I42. The anode-cathode voltage for the a plifier valve I42 is derived from a, secondary ding I43 on the transformer 38 by means of a rectifier valve I44, the outputrof which is impressed across a circuit, including a parallel capacitor I45 and resistor I45. The 'voltage across resistor I46 is impressed across the anodecathode circuit of the electric valve I42 and the plate resistor [42a connected in series. The cathode of the amplifier valve I42is connected directly with the positive terminal of the memory capacitor I00, and the control grid I4? is connected with a point of potential which varies with the outputof the regulating circuit and which is established by voltage dividing resistors I48 and I49 which are connected in series between the direct current supply conductor 63 and the output conductor 43 of the regulating circuit. As illustrated in the drawings, the control member I 47' is connected with an adjustable point on the voltage dividing resistor I49 through a current limiting resistor I50. The control member of valve I42 is connected with the anode thereof through a transient voltage suppression circuit including a series resistor I5I and a capacitor I52. The voltage across plate resistor I53 is, therefore, a unidirectional voltage which varies in accordance with the output of the regulating circuit 30', and this voltage is impressed on the phase shifting circuit IM to produce periodic voltages of peaked waveform which vary in phase position in accordance with changes in the supply circuit voltage. This circuit MI is similar to on-time phase shifting circuit 29 and comprises a pair of electric discharge devices I53 and I54 having 7 minals and the cathodes areconnected together series connected resistors i! and we. The primary winding itil or the transformer W6 is energized from the alternating current supply circuit M by means of the secondary winding ll or transformer 3%. In order to shift the phase oi. the anode voltages of valves B53 and W6, the transformer primary winding ifiu is connected icetween the mid-terminal of transformer secondary winding ll and the common terminal of a canacitor itil and adjustable resistor iiii which are connected in series across the end terminals of the transformer secondary winding ill, As will become more apparent from a consideration of the description of the operation of the system as a whole, it is desirable to retard the periods of conduction of electric valves lot and i543 of the ofi=-time phase shiftin circuit into that region or the supply circuit voltage occurring after the mniiniun heat setting which-in many appli= cations is approximately per cent of full heat.

The control members oielectric valves i513 and 156 are energized by a lagging component of alternatine current voltage supplied by a grid transformer lot and the variable unidirectional component or voltage appearing across resistor i 'licv or the amplifier circuit including valve 062.

ts illustrated the drawings, the cathodes of valves led and ltd are connectedv through the resistor 1162c to the mid terininal of the second= ar v Winding of transformer till, the end terminals or which are connected with the control members tlu'ouuh' suitable current limiting. resistors i533. The primary winding of transformer M52 is energized from the transformer secondary winding ll through a phase shifting circuit including resister 38d and capacitor its in much the same mannenes the anode transformer tilt is enersized. The relative magnitudes of the resistor and capacitor are chosen to give an alternating current component of voltage which lags the voltage impressed on the anodes of valves H53 and by a substantial angle. As will be apparent from the description of the on-time phase shifting circuit 29, the circuit l li is oncetive to produce periodic voltages of steep wave front across resistor it? at instants in the supply circuit voltage wave dependent upon the magni-- tude of the unidirectional voltage appearing across resistor i lil. This steep wave front voltage is utilized to controlthe conductivities oi a pair of electric valves 9% and it?! of the on-time filament supply circuit ilii. Ihe cathodes of electric valves toil. and Hill are connected top assoc-1ft and to the mid-terminal of winding are through voltage dividing resistor i222 which provides a component of negative tries, a conductor iii, the

/ opposite halves of a mid-tapped secondary wind-.

5 ing I15 of a transformer lid and a current limit- 0 circuit Mi, As previously mentioned, the dietill gethenand'the anodes thereof are connected,

respectively, with thes'econdary windings and its of a transformer lit having the primary winding ill thereof energized irons thesecondary winding ill of transformer 58 through a phase shifting circuit including a capacitor 972 and an adjustable resistor iii; to'impress on the anode cathode circuits of electric valves lit and till alternating voltages having substantially the same phase position as the anode-cathode voltages impressed on electric valves i553 and i541 oi' the ofi-time phase shifting circuit. The common cathodes of'electric valves I66 and ifil are connected with the midtap of transformer winding 61 and the anodes of these valvesare respecflu tively connectedwith the end terminals of the winding 6'! through transformer windings H58 and I69 and conductors 89 and 81. cults for the control members of electric valves"- I66 and 161 are completed from. the cathodes, 7

iii)

The clr-m 5 the tum-on voltage charge device 639 which is provided with a pair of discharge paths has the anodes thereof connected with the end terminals of the winding i715,

and the cathode thereof connected with the anode MS of switching electric valve it? so that during the on" period when the left-hand halfof elec tric valve Ml is conducting, the discharge device i til is made conducting to render the con= trol members or electric valves 56% and i671 mega tive.

When the regulating circuit is adjusted to sup ply full heat to the welding transformer, the roc ulator may attempt to advance the phase ahead of the power factor angle or the load circuit. This may cause only one of the main electric valves to conduct for a nurnhcr of cycles and this way produce unidirectional magnetization of the welding transformer. in. order to prevent this action, a circuit for limiting the angle or Q) advance or the peaked voltages produced by the on-time phase shifting circuit is provided. A8 illustrated, this circuit commie-es an electric dis charge devec iiil having a cathode connected with the cathodes or electric valves 38 and 82, and a pair of anodes connected respectively with through individual circuits each of which includes a winding i530 oi the transformer energized in accordance with the voltage oi the welding irans= former, and a wind ng not of the transformer 38 energized in accordance the supply circuit voltage of circuit ii. The sum oithe voltages of windings and idi is a measure oi the volt= age across the valves :12 i8 and by virtue oi the valve Hi9 this voltage is impressed on the control menihers of valves 8i 82 during any time that it is more negative than the alternat=.

ing current bias and voltage tild pressed on these control members by transfom= er winding 66 and conductor 32 and 63. This circuit operates to prevent the advancement of the voltages impressed on the control memberssigned to the assignee of the present application.

The features and advantages which character ize our invention will he hotter understood icy a brief consideration of the operation of the embodiment of our inventionillustratd in Figs. la andlb. in the preceding description, no reference has been made to any or the heater circuits for the cathodes understood; however, that suitable means for to the completion of the anode-cathode circuits 7 of the electric valves are also provided. With the alternating currentclrcuit ii energized, a. weld period mayrbe initiated [under the control of timer 25 by ClOSlDB' the switch 29. As scones from the output oi'the timer through the, conductor till, conductor til, the.

the control monitors of electric valves iii and 32 oi the electric valves, ancl none Q35 has been illustratedon the drawings. It will he ing.

circuit is impressed on transformer 24, the electric valves I2 and it will be rendered conductive.

at instants in the anode-cathode volta e waves established by the phase position of the periodic voltage of peaked wave form produced by the transformer 20. The phase position of this voltage is regulated in accordance with the current supplied to the load circuit and the heat setting established by resistors 86 and 86a by means of the regulating circuit 30. It will be assumed that the current during the first cycle -is higher than the value for which the regulator is adjusted and the anode-cathode voltage. impressed on the on-time filament supply valves 18 and the conductor 63 is connected with the ,cathodes of electric valves 3! and 32 of the on-time phase shifting circuit 29, these valves will become conductive at a later point in the anodecathode voltage wave thereof and will retard the phase of the peaked voltages produced by transformer 2d, and in this way reduce the magnitude of the welding current supplied to the transformas'raoco valve 100 is brought to the negative voltage of resistor ldZa which varies in magnitud across resistor- I83 disappears and the state of conductivity of the paths of discharge device Ill reverses; thatis, the left-hand half becomes nonconductive and the right-hand half becomes conducting. This also reverses the state of conductivity of valve I09; the left-hand half becomes nonconductive and the right-hand half becomes nonconductive. When the left-hand half of valve I09 becomesnonconductlve, the discharge path for memory valve I00 is interrupted and when the right-handhalf of valve W9 becomes conductin the control member IM of the charging electric conductor 63 and thecharging circuit of electric valvell'ifl is efi'ectively interrupted. Therefore, the voltage of capacitor we is maintained at. the value existing at the last instant of the period of energization. The voltage of the capacitor I00 is compared with the voltage of an adjustable potential on. voltage dividing resistor I69 which varies in accordance with the'output of the regulator circuit '3 and is impressed 0n the control member of the amplifyin electric valve 32 to produce a variable unidirectional voltag across in accordance with variations in the output of the regulating circuit to with respect to the voltage of.

capacitor Hi0. Variations in the magnitude of er it. If the current supplied during the first cycle is lower than that for which the regulator is adjusted, the converse of the above action takes place'and the phase of the voltages produced by the transformer 20 is advanced. During't-he time that the load circuit is energized, a positive bias is impressed on the left-hand control grid I29 of electric discharge device E ii by resistor I33. This renders the left-hand .half of discharge device ll'l conducting and the right-hand half of this valve is maintained nonconducting by the voltage of terminal lSii of voltage dividing resistors I37 and 38. Conduction by the left-hand half of. valve ll depresses the voltage of control member H6 of valve l9 substantially to the cathode voltage of valve ill and maintains. the righthand halfof discharge device Ht nonconduct- This'renders the charging electric valve wt for memory capacitor wt conductive under the control of the output voltage of the amplifying valve it to charge the memory capacitor I00 in accordance with the output of the regulating circuit 3. During this "on" time, the right-hand half of valve lllis nonconducting and the lefthand half of valve E9 is, therefore, maintained conducting to establish a discharge path for capacitor we to allow the voltage thereof to decrease during those periods that the regulator is operative to retard the phase of the voltages impressed on control members of electric valves l2 and 53. Thus, the capacitor ltd is charged and discharged during the periods of energization of the welding transformer to maintain thereon a voltage which is a measure of the phase position of the excitation voltages being impressed on the control members of valves l2 and i3. As soon as the period of energlzation established by the timer is is complete, the turn-on sinusoidal voltage of transformer 2d disappears and the combination of voltages impressed on the control members of valves l2 and it by the peaking transformer 2 and the hold-0E transformer. 22 is insufilcient to maintain these valves conducthe unidirectional voltage appearing across resistor l 52a control the ad time phase shifting circuit Ml to shift the phase of the peaked voltages impressed on the control members of elec-' tric yalves H65 and i6? ofthe off-time filament supply is to change the magnitude of the heatving current supplied to the filament of the regulating electric valve 64. In this way, the energization of the regulating valve 61% is varied during the ofi period ina manner to compensate for changes in the magnitude of the supply circuit voltage. For eXamp1e,if the supply circuit voltage increases during the "off period, the current supplied to the filament of regulating valve 54 by the off-time filament supply circuit'lsfi for a given phase position of the peaked voltages produced by transformer 75 will increase. This will render. the terminal es connected with the anode of the regulating valve ts more negative and will, therefore, render the conductor it more positive. This renders the control member of the amplifying valve leg-more positive with respect to the ,c'athode thereof which is maintained at a fixed potential by the memory capacitor ltd and increases the conductivity'of the valve [62. This results in an increase in the magnitude of the negative unidirectional voltage impressed on the control members of electric valves 53 and l 5 3 the off-timefilament supply. Thus when the initiating switch 26 is closed to establish a second spot, the regulating circuit. and particularly the filament of the regulating valve St is conditioned to supply exactly the, desired amount of current to the welding transformer, assumin the cons'tants of the load circuit have not changed between successive welds. From one point of view, the circuit of the present invention may be convoltage compensation during the off time is tive. As soon as the welding transformer is deenergized the positive bias voltage appearingaccomplished with respect to the supply circuitvoltage at the last instant of the preceding period of energization of the load circuit. By utilizing found undesirable in practice to connect directly across the anode-cathode circuits. of the gasfilled electric valves supplying the' load circuit, particularly when anode firing is used for immersion-ignitor type electric valves. This voltage appearing across these transformer wind- ,ings is impressed on a circuit including a resistor .2ld and acapacitor 2l5'in series to charge the capacitor 2I5 in accordance with the voltage appearing across electric .valves l2 and i3. The magnitudes of resistor 2H3 andcapacitor 2|?) are chosen to delay the charging of the capacitor sufiiciently to prevent electric valve 2% from being rendered conductive when the voltage appearing across the anodecathode circuit of electric valves l2 and i3 is a minimum. This circuit for'indicating the full-heat operation of the welder is described and claimed in my application Serial No. 506,612 filed concurrently herewith and assigned to the assignee of the present application. 4

The operation of the system described above is ingeneral similar to the operation of the embodiment illustrated in Figs. 1a and 1b. However, a brief consideration of the operation of this embodiment will serve to establish the difierences between the two modifications. When .the initiating-switch 28 is closed, the electric valves 52 and it are rendered conductive for a period dependent upon the operation of timer 2% and at instants in the anode-cathode circuit voltage dependent upon the phase position of the periodic voltage load current tends to increase above the value for which the regulator is set, the energization of the filament for regulating valve 5G is increased and the control member of amplifyingvalve let is rendered more negative., This renders the control member of the amplifier valve ltd more positive which renders the conductor did more, negative to retard, the phase of peaked voltage produced by the on-time phase shifting circuit 29.

dered nonconductive by operation of the timer 25, the voltage appearing across resistor=i33 disappears and switching electric valve it? is rendered nonconducting. This raises the cathode voltage of discharge valve I39 to remove the nega- As soon as the electric valves 62 and it are rentive bias from the electric valves use and ltl of the oil-time filament supply. Theelectric valveslt and 19 are maintained nonconductive during the ofi time by means of the negative bias impressed on the control members thereof by the adjustable tap IQ! of potentiometer E90. During the periods of deenergization of the load circuit,

the filament of the regulating electric valve 66' voltage of supply circuit H, any fluctuations in the supply circuit voltage will vary the energization of regulating valve 64 and modifythe output of the regulating circuit in accordance with the supply line fluctuations, which in turn changes the energization of the regulating valve at. In this way, the regulating circuit including the heated filament is kept in condition during the 0115" time so that upon energization of the load circuit the regulator is preconditioned at ap proximately the proper regulating point. The setting 'of the adjustable tap of potentiometer 186 may begmade in any desirable manner, and

we prefer to provide an ammeter'fl l i in the output of the on-time" phase shifting circuit 29. The reading of this ammeter during periods of energization may be noted and the adjustable tap on the potentiometer I86 adjusted so that the reading is just slightly less thanthe on-time reading and thus corresponds to a slightly retarded firing of valves 3| and 32. This will provide' regulation during the ofi time to a heat setting slightly below the heat setting of the welder circuit. Since-adjustment of the-movable tap of potentiometer I changes the cathode .voltage of the electric valves It and it of the on-time filamentsupply, the movable tap itl oi potentiometer 198, which determines the magnitude of the negative bias impressed on the control members of these valves, is simultaneous ly adjusted and assures these valves are maintained noncon'ducting during periods of deenergization of the load circuit.

While we have shown and described particular embodiments of our invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from our invention in its broader aspects, and we, therefore, aim in the appended claims to cover all such changes and modifications as fall within thetrue spirit and scope of our invention.

What we claim as new and desire to secure by,

paratus interconnecting said circuits includingelectric valve means having a control electrode, timing means for controlling said electric valve means for establishing periods of energization ,of said load circuit, excitation means for energizing said control electrode to establish the instant in the supply circuit voltage that said valve means is rendered conducting during said periods of energization comprising a regulating'circult, means responsive to the current supplied to said load circuit for energizing said regulating circuit, means for establishing an electrical quantity having a magnitude dependent upon the instant of initiation of conduction of said electric valve means during the latter portion of each period of conduction, and means for energizing said regulating circuit during periods of deenergization of said load circuit in accordance with variations in the voltage of said supply circuit by comparing the output of said regulating circuit with said electrical quantity. x v

- 2. In combination, an alternating current sup ply circult, a load circuit, electric translating apparatus interconnecting said circuits including electric valve means having a control electrode, an excitation circuit for said control electrode for determining the periods of energization of said load circuit and for determining the instant of initiation of conduction of said electric valve means during each cycle of energization of said load circuit comprisinga regulator circuit includ- 5. In combination, an alternating current supply circuit, a load circuit, electric. translating ing an electric valve having a, cathode of the ing a magnitude depen lent upon the instant of conduction of said valve means, means for energizing said filamentary cathodeduringperiods of deenergization of said load circuit in accordance with the voltage of said supply circuit, and means for varying the energization of said cathode during periods of deenergization of said load circuit as the output of said regulating circuit varies with respect to said electrical quantity.

3. In combination, an alternating current supply circuit, a load circuit, electric translating apparatus interconnecting said circuits including electric valve means having a control elec-- trode, timing means for controlling said electric valve means for establishing periods of energization of said load circuit, excitation means for energizing said control electrode to establish the instant in the supply circuit voltage that said valve meansis rendered conducting during said periods of energizatlon to maintain the current supplied to said load circuit constant comprising a regulating circuit, means responsive to the current supplied to said load circuit for ener. gizing said regulating circu t, means for establishing at the end of each period of energizetion an electrical quantity having a magnitude dependent upon the instant of initiation of conduction of said electric valve means at the end oi each period of conduction, means for energizing said regulator during periods 01' deener glzationof said loadcircuit in accordance with variations in the voltage of said supply circuit by comparing the output of said regulating circuit With said electrical quantity, and electronic switching means for transferring the energization apparatus interconnecting said circuits and including electric valve means having a control electrode, excitation means for controlling the energization of said control electrode to determine the cycles during which said valve means conducts and the instant in the cycles that conduction is initiated comprising a regulator circuit, means for variably energizing said regulator circuit in accordance with the current supplied to said load circuit during periods of energization of said load circuit, means for variably energizing said regulator circuit during periods of deenergization of said load circuit in accordance with fluctuations in the voltage of said supply circuit, and electronic switching means responsive to energization of said load circuit for rendering said last mentioned means inefiective during periods of energization of said load circuit.-

6. In combination, an alternating current supply circuit, a load circuit, electric translating ap paratus interconnecting said circuits and including electric valve means having a contro elec- Ttrode, excitation means for controlling th energization 01' said control electrode to determine the cycles during which said valve'means conduct .and the instant inthe cycles that conduction is initiated comprising a regulator circuit, means for variably energizing said regulator circuit in accordance with the current supplied to said load circuit during periods of ene'rgization or said load circuit to maintain the current supplied to said load circuit constant, means for variably energizing said regulator circuit during'periods of deenergization of said load circuit in accordance with fluctuations in the voltage of said supply circuiitand electronic switching means for transierring energization of said regulator from one of said regulating circuit from said last mentioned ing electric valve means having a control electrode, an excitation circuit for said control electrode for determining the periods or energizetion of said load circuit and for determining the instant of initiation oi conduction of said electric valve means during each cycle 01' energization 01' said load circuit comprising a regulator circuit including an electric valve having acathode of thefilamentary type, means responsive to the current supplied to said load circuit during periods of energization thereof for energizing said filament, means for establishing at the end of each period of energization an electrical quantity having a magnitude dependent upon the instant of conduction of said valvemeans, means for energizing said filamentary cathode during periods of deenergization of said load circuit in accordance with the voltage of said supply circuit, means for varying the energization of said cathode during periods of deenergization or said loadcircuit as the output of said regu energization of said- 7 load circuit. 4

0! said last twomentioned means to the other in accordance circuit.

'7. A. regulating circuit for regulating the cu1' rent supplied to a load circuit which is intermittently energized from an alternating current supply circuit comprising an input circuit and an output circuit, means for variably energizing said input circuit during periods of .energization of 'said load circuit in accordance with the current supplied to said load-circuit, means energized 1 from said output circuit for controlling the magnitude of the current supplied to said load cir-' cuit, means energized, from said supply circuit torcnergizing the input of said regulator during "v periods of deenergization of. said load circuit, and

means energized from the output or said regulator for controlling said last mentioned means to variably energize said inputcircuit'in accordance with voltage fluctuations of said supply circuit during the periods of deenergization or the 8. In combination, an alternating current supply circuit, a load circuit, electric translating apparatus interconnecting said circuits including electric valve means having a control electrode, timing means for controlling said electric valve means to'establish periods of lenergization of said load circuit, excitation means for energizing said control electrode to establish the instants in the supply circuit voltage that said electric valve means is rendered conducting to maintain the current supplied to said load circuit substantially constant comprising a regulating circuit-havinginput and output terminals, means for energizing said input terminals in accordance with the cur with the energization of said load a s fhr establishing periodsor en rent supplied to said load circuit during mriods oi 'energization thereof, means energized from saidalternating current supply circuit for ,ener- J sizing-said inputterminals during periods of deenergization of said load circuit, and me sponsive to the voltage of the output to a said regulating circuit for controlling said last mentionedmeans to adjust the output of the-regulator in a manner to compensate for supply circuit voltage fluctuations.

. 9. In combination, an alternatingcurrent sup-- plycircuit, a load circuit, electric-translating apme a 0,090

paratus interconnecting said circuits including electric valve means having a control electrode. 11 t means for controlling said electric valve means for establishing periods of enertion of said loadcircuit, excitation means for once control electrode to establish the instants in the supply circuit voltage that said electric valve means is rendered conducting d said Periods of enertion comprising a regulating.

circuit for producing a unidirectional voltage, means responsive to the current supplied to said load circuit for variabLv ener said regulating circuit to vary the magnitude of said unidirectional voltage, a phase shifting circuit for ene-" 1.; said control. electrode and energized in "said second phase shifting circuit in accordance with the output of said regulating circult,

i g circuit for contrc the energization oi said regulating circuit during periods of deepergization of said load circuit. v 10. In combination, an alternating ct supply circuit, a load circuit, electric translating apparatusinterconnecting said circuits inclug, electric valve means he a control electrode,-

' it means for controlling said electric valve ergization of saidload circuit, excitation means for one w said control electrodes to establish th i I .the supply circuit voltage that-said e ectrlc'valve means. is rendered conducting during said periods of energisation comprising a re cirsupply circuit and fhr retarding the p of the voltage impressed on said electric valve with respect to the voltage impressed on said electric valve means, and means for varying the conductivity of said electric valve 'in accordance with the output of said regulating circuit during perlods of deenergization of said load circuit to control the energization of said regulating circuit.

11. In, combination, an alternating current supply circuit, a load circuit, electric translating apparatus interconnecting said circuits including electric valve means having a control electrode, timing means for controlling said elecvalve means for establishing periods of energizationoi said load circuit, excitation means for energizing said control electrodes to estaband means responsive to said second phase vrdance with said unidirectional voltage, a second phase shifting circuit, means for enerapparatus intercoing said circuits inclu circuit for directional voltage, 111 for one said regulating circuit in accor m with the current supplied to said 1 circuit, a capacitor,

[means for controlling the charge on said capacitor during periods of enertion of said loadcircuit so that the voltage of said capacitor is a measure of the conductivity of said electric valve means, a circuit for gene! said regulating circuit during periods or deenergization of said load circuit inclu an electric valve having the anode-cathode circuit thereof enersized from said alternat current supply circuit, and means for controlling the conductivity oi said electric valve means in accordance with variations in the output voltage of said regulating circuit with respect to the voltage of said capacitor during periods or I deenergization of said load circuit.

12. In combination, an alternating current supply circuit. a load circuit, electric transla electric valve 1 ha a control elect timing meansfor controlling said electric. valve means for estab periods of energisation oi said load circuit, excitation mans for enercult for producing a unidirectional vole, means responsive to the current supplied to said iting circuit,

for supp said control electrodes toestablish the instants in the eupp yfcircult voltage that d electric valve means is rendered conducting during said periods of energization comp a regulating circuitfor producing a unidirectional voltage, me for ans 2 in 1; said regulating circuit in accordance with the current supplied to said load circuit, a capacitor, is a r: vi and discircuits for said'capacitor for mainthe on said capacitor which isat w periods oi auction at fat at d measur i the positioniot elecnicvalve means. initiation of conduction of said n wforinterrupting said-cha and discharging circuits at the end or each period of energization. and means responsive to variations in the output voltage of said, regulator oircuit'with reheet tosaid capacitor voltage for ergizing said regulator circuit d 1 1 deenergizationioi said load circuit.

13. In combination, a load circuit,

sri timed applicati of current to said is circuit including 1;. of vole, e, capacitor, a

eluding an electric valve for controlling the not said char ing anddischarsins circuits simul-., taneously conductive whereby the charge on said; capacitor is adjusted during certain intervals and maintained constant during other intervals 1 lilh the instants in the supp y circuit voltage that said electric valve means is rendered coni tivity cha-oi said capacitor from said sourw of LII. circuit shunting said capacitor and including an electric valve, elec- I tric discharge means inclu a pair of disvoltage, a disclh charge paths connected to control the conducor the electric valves in said I'i r and circuits, means for nor n renderdisch ing on i said discharge paths conducting and,

the other of said discharge paths non-conducting to maintain both charging and discharging circuits inefiective, and meansresp ve to said timing means for reversing the sta tivity oi said discharge paths to render the valves determined by said timing means.

14pm combination, a load circuit, electric translating apparatus iorsupplying timed ap ications of current to said load circuit, afcapaci tor, means for charging ld capacitor in 9. voltage dependent upon the-value oian operating means meanaasource circuit inof conduc- 2,878,545 condition of said translating apparatus during cy'clesoi' energization of said load circuit, a discharge path connected in parallel with said capacitor and including an electric valve having a control member, means for energizing said control member to render said discharge path conductive only during periods or energisation of said load circuit so that the charge on said capacitor is adjusted in either direction as .the

magnitude of said operating condition variesand for maintaining the charge on said capacitor during periods of deenergization ata value corresponding to the value of said condition at the end or the preceding periodor energlzation. 1

15. In combination, a load circuit, electric, translating apparatus for supply timed applications of current to said load circuit, a ca- .pacitor, means for charging said capacitor to a 'cuit, said translating apparatus including timing voltage dependent upon the value or an opersaid load circuit so that the charge on said capacitoris adjusted in either direction as vthe magnitude or said operating condition varies and for maintaining the'charge on said capacitor during periods oi de'energization at'a mum responding to the value of said condition at the end of the preceding period of energization.

18. In combination, a supply circuit, electric translating apparatus. including a load circuit connected for energization from said supply cirmeans for enacting timed applications of current to said load circuit, a. capacitor, means including a unilaterally conducting device to! charging said capacitor to a voltage dependentupon the value of an operating condition of saidtranslating apparatus during cycles of energlza-' tion of said load circuit, a discharge path connected in parallel with said capacitor and including an electric valve having a control member, means for energizing said control member to render said discharge path conductive only during periods of energization of said'load circult so that the charge on said capacitor is adjusted in either direction as the magnitude'oi said operating conditionv varies, and means re-l sponsive to said timing means for rendering said valve nonconductive to maintain the charge on u said capacitor during periods of deene tion 'at a value -corresponding to the value 1 said condition at the end of the preceding pe energization." BENJAm COOPER.

ORR-m WHHVINGBTON. 

